Industrial By-Products Upgraded Into Fuel

"Butanol is a very energy-efficient alternative and, like ethanol, lends itself well for industrial-scale production," says Professor Ulla Lassi from the University of Oulu, who has been working on a research project investigating the use of biobutanol as a transport fuel. Butanol production is a microbiological process where raw material is converted into sugars and further processed using microbes. The microbes efficiently turn carbon compounds into butanol. Butanol contains more carbon than ethanol does and is therefore also more energy-efficient.

Lassi's project has also studied the production of butanol via chemical synthesis, which uses novel catalyst materials to convert compounds such as glycerol, methanol or ethanol into alcohols such as butanol, pentanol and alcohol mixes. These are directly suitable as liquid fuels. According to Lassi, using glycerol in fuel production could be quite cost-efficient, as it is a by-product of biodiesel.

There are a number of challenges in the microbiological production of butanol. One of the main challenges concerns the digestion of the raw material to fermentable sugars. In addition, the multi-stage fermentation is in itself a very complex process. Another major challenge is that the fermentation process is inhibited by high solvent contents, which combined with instability in solvent production may also cause a drop in microbial activity.

Lassi explains: "Recent breakthroughs in butanol fermentation techniques have partly solved these problems. However, if we want to produce new liquid fuels, we need completely new chemical synthesis routes and catalyst development."

The research project investigating the production of biobutanol involves researchers from the University of Oulu and Åbo Akademi University.

Once landfill gas, now fuel

Another research project within the SusEn research programme has looked at the use of biogas as a transport fuel. As a joint Finnish-Chilean effort, the researchers studied the upgrading of landfill gas into fuel. "In recent years, interest in using biogas technology in the utilisation of industrial by-products for energy purposes has increased considerably. Some countries have already introduced this technology on a large scale," says Professor Jukka Rintala, the principal investigator of the project.

Biogas can be produced from many different materials ranging from biodegradable waste to energy crops. "The biogas produced in this process is a versatile source of energy. It can be used for heat and electricity, be processed into vehicle fuel or fed into the natural gas grid. In addition, the residual material, the so-called digestate, from the process can be used as fertilizer or soil conditioner," Rintala explains.

Methane derived from biogas has been shown to be one of the most suitable candidates for use as biofuel, thanks to its sustainable production chain. Methane also meets the EU's criteria for sustainable biofuels, which will take effect in a few years' time.

The experiments in Rintala's project were carried out at the Mustankorkea Waste Treatment Facility in Jyväskylä and they particularly focused on the fate and removal of trace compounds of biogas. "Biogas can be used as a biofuel once its methane content is raised above 95 per cent. In our research, we used water absorption, which yielded a methane content of 80-90 per cent. The rest is carbon dioxide and nitrogen."

Nitrogen does not cause any damage to car engines, but it does lower the energy content of biogas. "To reach a higher methane content through this process, we should prevent the access of nitrogen in the gas collection system in the landfill. Carbon dioxide does not damage engines either, but it lowers the energy value of biogas," says Rintala.

Rintala would like to see more research on the effects of process parameters on the costs of biogas upgrading and the effects of pressurisation on compound removal. "As a rule, the only criterion for biomass is that it can be broken down by microbes under oxygen-free conditions. Of course, the composition of feedstocks does affect the composition of the biogas produced and also the chosen method of purification. Landfill gases are generally thought of as being the most difficult ones to upgrade into fuel."

How birds avoid crashes

The secret of how birds zip flawlessly through narrow spaces without crashing into obstacles has been unlocked by Australian scientists.

Their discovery could be used to design ‘bird-safe’ buildings and windmills, and improve the versatility of pilotless aircraft.

Researchers at The Vision Centre have found that birds weave rapidly and safely through dense forests and narrow corridors by using their eyes to sense the speed of background image flow on both sides and adjust their flight according to it.

“As animals travel forward, things that are close seem to speed by, and things that are farther away seem to travel more slowly,” says Professor Mandyam Srinivasan from The Vision Centre and The University of Queensland, whose team made the discovery. “It’s the same for birds. We found that they try to achieve a safe ‘balance’ by ensuring that the background images are passing at the same speed in both eyes.

“This means that if the bird flies closer to obstacles on one side, the near eye will see things passing by faster while those seen by its other eye will pass more slowly. This imbalance prompts the bird to veer away to even out the speed of image flow in both eyes.”

To find out how birds navigate through narrow passages and away from danger, the research group trained budgerigars to fly along a corridor with walls lined with horizontal or vertical stripes, says Dr Partha Bhagavatula of The Vision Centre and The National Vision Research Institute.


“We found that birds fly the fastest when both walls are lined horizontal stripes, because the stripes are parallel to the bird’s flight direction, and the birds don’t ‘see’ a strong image flow in the background,” Dr Bhagavatula says. “But when both walls have vertical stripes, birds slow down significantly due to the strong image motion, which shows that birds also regulate their flight speed according to what they see.”

When the walls were set up with different orientations – one with vertical and the other with horizontal stripes, the group found that birds flew significantly closer to the horizontal stripes.

“As vertical stripes project a stronger image flow to their corresponding eye, they veer away to restore the balance between the flows experienced by their two eyes,” says Dr Bhagavatula. “This was also demonstrated when one wall was left completely blank. Then the birds flew very close to, and occasionally collided with, the blank side.”

Prof. Srinivasan says that flight behaviour in birds is very similar to insects such as honeybees, bumblebees and flies: “This suggests that this principle of visual guidance may be shared by all day-active flying animals.

“Furthermore we believe these findings can contribute to the technology of guiding unmanned aerial vehicles where aircraft have to fly through obstacles in cluttered environments, or through canyons and gorges, or under bridges.

“Another potential application is the design of urban structures that are more bird-friendly to minimise the risk of bird fatalities through collisions with window panes. We can also think about decorating windmill blades with patterns that generate motion signals to repel birds.”

The group’s paper “Optic flow cues guide flight in birds” by Partha Bhagavatula, Charles Claudianos, Michael Ibbotson and Mandyam Srinivasan has been published in the latest issue of Current Biology.

Polymer Composites Containing Nanotubes (CNTs)

1. Introduction
Polymer composites containing carbon nanotubes (CNTs) have emerged as advanced multifunctional materials in view of exceptional mechanical, thermal and electrical properties associated with CNT [1]. They have become attractive structural materials not only in the weight-sensitive aerospace industry, but also in the marine, armor, automobile, railway, civil engineering structures, and sporting goods industries because of their high specific strength and specific stiffness. Different polymer/CNT nanocomposites have been synthesized by incorporating carbon nanotubes (CNTs) into various polymer matrices, such as polyamides [2], polyimides [3–5], epoxy [6], polyurethane [7–8] and polypropylene [9–11]. The presence of the nanotubes can improve the properties of polymers as well as add multi-functionality to polymer based composite systems [12-14]. Among the resins, epoxy resins have good stiffness, specific strength, dimensional stability and chemical resistance, and show considerable adhesion to the embedded filler [15].
Many studies have been conducted on multiwalled carbon tube (MWNT) based composites earlier and recently on aligned carbon tube (ACNT). MWNT composites have shown improved result in tensile modulus and yield strength [16]. However some studies reported decrease in flexural strength and pull out of CNTs in those composites [17]. In order to detect orientation and deformation of the CNTs in the nanocomposites, the tensile behaviour of both random and aligned MWNTs/Polystyrene nanocomposites was investigated by Thostenson and Chou [18]. They found the aligned CNTs composites showed more improved mechanical properties than random CNTs composites. Therefore, the comparison of different CNTs to obtain an efficient composite is very important. The purpose is to compare the suitability of these fillers in a polymer matrix that can be aimed for structural applications in aerospace/ automotive industries. In view of this in the present study, two types of nanotubes were dispersed in epoxy matrix. The mechanical properties of CNTs reinforced epoxy composites were measured using the flexural and
hardness tests. Fracture behaviour and crack propagation of the nanocomposites are studied by scanning electron microscopy. The pure epoxy samples were also prepared and subjected to the tests for comparison.
2. Experiments
A. Materials
Multiwall carbon nanotubes (MWCNTs) used for the preparation of nanocomposites was obtained from MER corporation, USA. They are produced by arc plasma method (purity 95%, length 1-5 μm and diameters 20-70 nm). SEM morphology of the products (Fig. 1) was carried out with a "JEOL JSM-6480 LV Scanning Microscope". They are highly entangled and randomly oriented.
Fig.1 SEM of Random carbon nanotubes (RCNTs)
Aligned carbon nanotubes (ACNTs) used for the preparation of nanocomposites was obtained from ARCI, Hyderabad, India. They are produced by chemical vapor deposition method diameters 10-20 nm. SEM morphology of the products (Fig.2) was carried out with a “JEOL JSM 5410 Scanning Microscope".
Fig.2 SEM of Aligned carbon nanotubes (ACNTs)
Epoxy polymer matrix was prepared by mixing epoxy resin (Ciba-Geigy, araldite LY-556 based on Bisphenol A) and hardener HY-951 (aliphatic primary amine) in wt. ratio 100/12. Epoxy resin (5.3-5.4 equiv/kg) was of low processing viscosity and good overall mechanical properties.
B. Nanocomposite preparation
Two types of nanocomposites involving Randomly oriented multiwalled carbon nanotubes (RCNTs) and aligned multiwalled carbon nanotubes (ACNTs) were prepared. First the nanotubes of both types were treated in ethanol for the deagglomeration of the tube bundles. The treated tubes (0.5 %) were then added to the epoxy resin and sonicated for 2hrs at room temperature.Hardener was added to that mixture and stirred. Then the mixture was poured into a mold and cured under vacuum at 900 C for 10 hrs. Pure resin samples have also been prepared for comparison purpose.
C. Flexural strength test
From each sample, five rectangular specimens were taken for three-point bend test as per ASTM D790 (width=2.7cm, thickness=0.7cm, span=11.2cm, length=12cm). Flexural tests were carried out at ambient temperature using Instron 1195 keeping the cross-head speed 2 mm/min. Flexural modulus of each sample was determined from the average value of five specimens.
D. Hardness of nanotube composites
The hardness of all samples was measured using a micro-hardness tester. A total of 10 points on each of the nanotube composites were measured in order to get average readings. The unit and magnitude of the hardness are defined by Vickers hardness, Hv and determined by measuring the average diagonal length, d of the indentation (mm).
E. Surface topography characterization
Scanning electron microscope (JEOL JSM-6480 LV) was used to conduct the dispersion behaviour and fracture surface topography characterization. After mechanical test fracture surfaces were coated with a thin platinum layer.
3. Results and Discussion
A. Flexural measurements
Flexural modulus of pure resin, RCNT composite & ACNT composite are
shown in Fig.3. Both the composite samples are showing greater modulus than pure resin sample that is attributed to the high mechanical strength of CNT. Flexural Test02004006008001000EpoxyEpoxy/RCNTEpoxy/ACNTSample TypesFlexural Modulus in MPa
Fig 3 Flexural moduli of resin as well as composite samples
The flexural modulus was found to be 136.86 MPa in case of epoxy/RCNT composite which is about six times than the flexural modulus of plane epoxy sample (24.52 MPa). Increase in modulus is more pronounced in epoxy/ACNT composite i. e. 837.42 MPa which is more than six times that of epoxy/RCNT composite and thirty four times that of epoxy sample. This may be due to efficient load transfer from matrix to aligned CNT in
axial direction. Local stiffening due to nanotubes results in improved load transfer at the fibre/matrix interface [18]. It had been reported that the increase in elastic modulus between the random and aligned nanocomposite is a consequence of the nanotube orientation, not polymer chain orientation.
B. Hardness measurements Microhardness Test 0102030405060EpoxyEpoxy/RCNTEpoxy/ACNTSamplesHardness in MPa
Fig. 4 Hardness of epoxy and epoxy/ nanotube composites
A considerable enhancement of hardness is observed by the nanocomposites in comparison to pure resin sample (Fig.4). Pure resin samples showed hardness of 12 MPa. Epoxy/RCNT had hardness value of 18 MPa which is 50% more and epoxy/ACNT had 49 MPa that is about four times that of epoxy sample. High strength and long nanotube reinforcements may result in forming a network structure that improves the hardness of the composites.
C. Surface topography analysis
The investigation of the fractured surfaces to analyse the micro deformation and crack propagation mechanism has been carried out using Scanning electron microscope (SEM). The micrographs corresponding to nanocomposites obtained by incorporating RCNTs and ACNTs are presented. From Fig.5a & b, the fracture surface of epoxy/RCNT appears to be rough than epoxy/ACNT composites.
Fig.5 Fracture surface of (a) epoxy/RCNT (b) epoxy/ACNT composite sample
The resultant failure mechanism of the epoxy/RCNT interface was analysed by observing the crack propagation regions within the composite (Fig. 6a). An agglomeration of several carbon nanotubes was observed in the fracture surface near the crack region. At a low stress level, the agglomerated particle increases the stiffness of the material, but at a high stress level, the stress concentration caused by the agglomerated particle initiates a crack, which make the sample fail quickly. Some nanotubes were observed to be pulled out which might be the result of a poor interfacial bonding between the nanotubes and matrix. Therefore, the nanotubes inside the composites could not take
up the load, which resulted in the decrease of flexural strength of the nanotube composite beams [19]. In comparison to that in case of epoxy/ ACNT composites, no crack was observed though the surface was seen to undergo less intensive fracture with smaller crack lengths in vertical direction (Fig. 6b).
Fig.6 Crack features of (a) epoxy/RCNT (b) epoxy/ACNT composite sample
Higher magnification showed a crack interacting with the nanotube reinforcement. RCNT matrix pullout was observed along with extension and bridging of RCNTs across the crack (Fig.7a). In epoxy/ACNT composites, the cracks were spanned by the nanotubes causing enhanced resistance to the crack propagation process. The bridging of the nanotubes as a mechanism of inhibiting the crack initiation in polymer and ceramic based nanocomposites has been well illustrated in literature [20-24].
Fig.7 Bridging mechanism of (a) epoxy/RCNT (b) epoxy/ACNT composite sample
From the above discussion, the evident difference between fracture surfaces indicated that the reinforcing role of nanotubes in the two kinds of polymer nanocomposites was different. The mechanical tests described above further supported this.
4. Conclusions
All the composite samples demonstrated enhanced mechanical properties than pure resin samples that were attributed to addition of high strength nanotubes. In addition, aligned nanotube composites resulted in significantly improved flexural modulus and hardness indicating that there is efficient load transfer between the polymer matrix and the nanotube reinforcement along axial direction. Reduction in flexural modulus and hardness value in epoxy/ RCNT composites was due to formation of agglomerates of nanotubes inside polymer matrix that reduced reinforcing effects of the CNTs by acting as flaws in the resin. Investigation of fracture surface in nanocomposite revealed that narrower crack-tips underneath the advancing cracks were more efficiently bridged by the nanotubes in epoxy/ACNT resulting in an increased resistance against crack propagation.

Applications Abound For Nano Field

“If you ask 10 people what I study, you may get 10 answers,” says Krystyn Van Vliet. That’s because the general phenomenon she explores — how a material’s mechanical properties, such as stiffness, can affect its chemistry, and vice versa — is applicable to so many disciplines. Van Vliet’s work has already, for example, led to important insights on everything from the formation of blood vessels to the structural dynamics of cement.

Key to her approach: studying these chemomechanical interactions at the nanoscale, or billionths of a meter.

Van Vliet, the Paul M. Cook Career Development Associate Professor of Materials Science and Engineering and Biological Engineering, is at the forefront of a relatively new field called chemomechanics. The tools that can probe materials’ mechanical properties at the most basic level of atomic features have been around only since the early 1990s.

Van Vliet recalls needing to travel to Lawrence Livermore National Lab to run experiments for her MIT doctorate because the Institute didn’t have the equipment. Now, she’s faculty director of the Department of Materials Science and Engineering’s NanoMechanical Technology Laboratory, “which is filled with these machines.”

Van Vliet first used these tools, coupled with computer simulations, to show how a stress or force can initiate a defect in an otherwise perfect crystal of metal. Such work is important as devices get smaller and smaller — a seemingly minuscule flaw can compromise their performance.

She’d always had a strong interest in biology, however, so before joining the MIT faculty she spent her postdoc years in a lab at Children’s Hospital. “I felt that there were measurements I could take down at the nanoscale to explore how mechanics might affect cancer biology and
vascular biology,” she says. “I don’t pretend that I knew how I was going to do that, but it seemed like it should be possible.”

She succeeded, and biology is now a major focus of Van Vliet’s lab. “Small changes in the chemistry of the interface [between a cell and the material it is next to] can affect the mechanical adhesion of the cell to that material, for example,” says Van Vliet. Similarly, “small changes in the mechanics, like the fact that the periphery of a tumor is stiffer, can change the biochemistry — how quickly, for example, enzymes can affect the speed of certain reactions.

“It’s that back-and-forth between chemistry and mechanics that interests me,” she says.

Among other advances, she and colleagues have shown how certain cells surrounding capillaries may use mechanical forces — contractions — to initiate angiogenesis, or the growth of new blood vessels, a process key to wound healing and the growth of cancerous tumors. The team is currently exploring how these contractions affect the growth rate, shape, and chemical secretions of the cells key to angiogenesis.

Van Vliet emphasizes, however, the range of projects in her lab. These include not only studies of cells, but of inorganic materials like new scratch-resistant coatings for cars, and even polymer nanocomposites that replicate the mechanical response of real human tissues. So, for example, the Army could develop a new protective garment without testing on a live body.

“So many amazing discoveries have been made at MIT,” says Van Vliet. “It’s inspiring just to be around all that history of great thinking and enthusiasm for learning.”

I C engine efficiency

Improving IC Engine Efficiency
Today’s efficiency situation:
FUEL 100%
PUSHING THE PISTONS 35%
OVERCOMING ENGINE FRICTION AND PUMPING THE AIR AND FUEL
(typical US driving condition) 20%
Are we stuck with ~20% auto engine efficiency?
What can be done?

1. Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency. In the old days, under cruising conditions, the engines always ran lean – about 15% excess air -- this was economical. So what happen to change this? The problem is the three-way (CO, UHC, NOx) catalyst used on engine exhausts. This only works if the engine air/fuel ratio (by mass) is stoichiometric (chemically correct). For gasoline this ratio is 14.6:1. The engine computer, acting in concert with the engine air flow sensor, electronic fuel injectors, and exhaust oxygen sensor, maintains the stoichiometric ratio for most of your driving. Only at this ratio can the catalyst both oxidize the CO and UHC (to CO₂ and H₂O) and chemically reduce the NOx (to N₂). (UHC = unburned hydrocarbons.) What humankind needs is a lean-NOx catalyst. Then we could have increased efficiency and continue to be clean!
Also needed are ways to improve lean flammability in gasoline engines. That is, the ability to burn real lean is limited by the fuel. If the gasoline-air mixture is too lean, the flame will not have enough speed to get across the cylinder in the time permitted by the engine RPM the driver wants, or the flame will not even start – the cylinder misfires, and then the catalyst has to oxidize a huge amount of UHC and thus may overheat (which might mean you have to buy a new catalyst). Background: A first course on thermodynamics may teach the efficiency of the Otto cycle (which is the ideal cycle used to simulate the gasoline spark ignition auto engine). Such a course would derive the following equation for the Otto cycle efficiency:
h = 1 – 1/r_v^g-1
The compression ratio of the engine is r_v. Actually, this is a volume ratio. It is the ratio of the volume in a cylinder when the piston is at the bottom of the cylinder to the volume in the cylinder when the piston is at its top position: r_v = V_bottom/V_top. Most auto engines have compression ratios in the 9 to 10.5 range. We note: the higher the compression ratio, the higher the efficiency! The g parameter is the ratio of the specific heats, ie, the constant pressure specific heat over the constant volume specific heat. In practical terms, the higher the g, the higher the efficiency. A gas such as helium or argon, composed only of atoms, has the highest g possible, 1.67. Room air on the other hand, being mainly composed of O₂ and N₂ molecules has a g of 1.4. Fuel vapor has g less than that of air. The mixture of air and gasoline vapor inducted into the engine has a g of about 1.35. As this mixture is compressed and heated during the compression stroke, its g drops to about 1.33. Upon combustion (when the piston is near its top position), the fuel is oxidized to CO₂ (and some CO) and H₂O, and g drops further. It drops into the 1.20-1.25 range. The overall, effective g for the whole cycle for use in the efficiency equation above is about 1.27. The rule of thumb is: the greater the complexity of the molecules, the lower the g. The lower limit is 1. Argon and helium atoms only translate, that is, they move along straight paths until they encounter another atom. Room air molecules translate and rotate (about 2 of their axes). Hot air starts to vibrate (as two nuclei connected by a spring). Molecules of fuel vapor have a lot of opportunity to vibrate, even at room temperature. The products of combustion vibrate. However, only the translation of the molecules PUSHES the piston. The other modes of molecular motion do nothing for pushing the piston. Thus, as g drops (indicating more vibration of the molecules), h drops. A lean engine (ie, an engine with excess air) has a cooler combustion process and more air relative to fuel than the typical engine with a chemically correct mixture. Thus, its g is higher, and its h is greater. Plug g = 1.27 into the efficiency equation above, assume r_v = 10, and you get h = 0.46. Multiply this by about 0.75 to account for real cycle effects (such as the time it takes to burn, heat losses to the coolant, and exhaust valves that open before the piston fully reaches bottom position) and you have h = 0.35. This is the efficiency (given above) of using the chemical energy of the fuel to push the pistons. Multiply this by the mechanical efficiency of the engine, which accounts for the mechanical friction in the engine and for the air (and fuel) pumping work that has to be done, and you have the final, or overall efficiency of the engine. Of course the mechanical efficiency varies with driving conditions. The higher the RPM of the engine, the greater the friction loss. The more closed the throttle (ie, the farther your foot is off the pedal), the higher the pumping loss. For typical US driving, the resultant overall efficiency of the engine is about 20%. Note, your pedal is not really a gas pedal, it is an air pedal! Add the tranny and real axle mechanical friction losses (or the transaxle friction losses) and the drain of a few essential accessories, and you arrive at a 15% fuel-to-wheel efficiency for the typical auto driven in the US.
2. Higher compression ratio. Here, we are limited by autoignition of the gasoline – knock. That is, if the gasoline engine compression is above about 10.5, unless the octane number of the fuel is high, knocking combustion occurs. This is annoying and if persistent, damage to the engine can occur. Thus, gasoline engines are limited in their efficiency by the inability of the fuel to smoothly burn in high compression ratio engines.
However, the diesel engine is not subject to this limitation. It runs at high compression ratio. In part, this explains its high efficiency. It also runs lean, and its pumping work is low, further increasing its efficiency over the gasoline engine. Humankind needs quiet, smoke-free, odor-free diesels!
3. We need new cycles put into practical use. An example is the Atkinson cycle. This has a smaller compression ratio than expansion ratio. This means T_C is reduced since the burnt gas cool as they expand, making the cycle efficient. We throw away less waste heat via the exhaust.
4. Run the engine at optimum conditions, meaning low friction (modest engine speed) and low pumping work (air throttle more open). Try to approach the "pushing-the-pistons" efficiency of 35%. This already is happening in some stationary piston engines – large, slow, piston engines used at pipeline compressor stations, for example. Also, this is an important characteristic of the engines used in the hybrid gasoline-electric vehicles. Let the gasoline engine in the hybrid gasoline-electric power plant only run with good throttle opening and modest RPM. An example of one type of commercially available hybrid engine (a "parallel" type) is found at:

(http://prius.toyota.com/technology/hybrid.html).
Note the hybrid power plant also recovers some of the kinetic energy of the vehicle, by letting this KE drive an electrical generator (during braking). The electrical energy is stored in the batteries. (Normally, this KE is dissipated as heat in the brakes.) An inverter is used to convert DC electricity from the batteries to AC electricity needed by the electric motor and created by the generator.

______________________________
The table below compares the "well-to-wheel" efficiencies of several auto power plants. "Fuel Prod" means the energy efficiency of extracting, refining, and transporting the fuel. "Eng" means the "fuel-to-wheel"efficiency of the vehicle. "Gas" means gasoline engine. "FC-HC" means a PEM fuel cell with a gasoline-to-hydrogen reformer on board. (PEM = proton exchange membrane fuel cell, the fuel cell type that has been getting most of the attention for auto and home use.) "FC-MeOH" means a PEM fuel cell with methanol-to-hydrogen reformer on board. (The methanol is produced at a refinery by steam reforming natural gas – thus it is a "fossil fuel".) "Ems" means emissions (CO, UHC, NOx) impact. The ratings are "low" (where we are now for autos), "ultra low", and super low".

Cadillac V16 engine

The Cadillac V16 engine was a type of automobile engine produced in the 1930s. Cadillac produced two of only three production, gasoline-fueled V16 engine models in history. Both were used in the Cadillac V-16 automobile, the first from 1930 until 1937, and the second between 1938 and 1940. The company has twice attempted to build a new V16 engine, once in the 1980s and again in 2003, but these have yet to be put into production.

The only other 16-cylinder automotive engines ever attempted were Bugatti's 1915 U16, Marmon's V16, and Cizeta-Moroder's V16. A modern, quad-turbocharged W16 engine was used in the EB 16/4 Veyron built by the new Volkswagen-owned Bugatti in the 2000s.