# Questions tagged [engines]

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### Heat engines in N2/O2 vs noble gas/O2 atmospheres - which is more efficient?

Let's say you have a large test chamber where you can fill its contents with any gas mixture of your choice. In this instance two efficiencies of interest would be specific power output (kW/kg fuel ...
20 views

### Free body diagram of a reciprocating engine

this is a free-body diagram for an engine's slider-crank mechanism . It basically shows the inertia forces acting on the piston,cylinder-wall,crank,and connecting rod. I can't understand why the links ...
58 views

### Throttle position as a function of engine torque and speed

In the figure attached showing the throttle position versus an IC engine produced torque, I didn't understand why does the torque value at a specific rpm vary for different throttle positions. My ...
52 views

### Why is Scotch-Yoke mechanism not used for internal combustion reciprocating piston engines?

Regarding piston acceleration variations due to the geometric nature of crankshaft and connecting rod motion, in relation to connecting rod length and bore to stroke ratio. Why is Scotch-Yoke ...
1 vote
130 views

### Why did WW2 torpedoes use wet-heater engines instead of piston engines?

I understand how both types of engines work, but I don't understand the pros and cons of using one vs the other. Why are wet heater engines so suitable for torpedoes, but seemingly no other ...
54 views

### Wheel's torque and differential gearbox

I know that the differential gearbox is providing a torque to the wheels; as the relation in the figure indicates : Tw (wheel torque) = Td (differential torque) × (ηd×nd). Where nd:is the differential ...
45 views

### Shifting Between Gears To Achieve Higher Acceleration

If the car's acceleration is higher when the wheel's angular acceleration is higher(tangential acceleration=alpha x radius). Why are higher gears not used to accomplish the acceleration of the car ...
41 views

### Question about engine reaction torque from gas forces

in the figure below the reaction torque equation is given by Fg41.x trying to rock the ground plane about the O2 pivot due to gas forces . My question is if the piston with the cylinder whole assembly ...
156 views

### How friction between stator and rotor is dealt with in an electric engine/motor

This YouTube video https://www.youtube.com/watch?v=nlG2dsYRagI shows how an electric engine is made but I don't understand how friction between the stator and rotor is dealt with. At 3:50, we see the ...
72 views

### Question about torque in car engines

Sometimes people say "The engine of Car A has a higher torque than Car B with both having the same horsepower" My question is : if both cars are equal in horsepower can't we just avail this ...
31 views

### How to sense off-idle in internal combustion engine?

What is the simplest way to sense off-idle in an internal combustion engine? I am currently focusing on roadgoing and tractor, but would like as general-case a solution as possible. Priority is on ...
64 views

### Where does all the inherent vibrations in an internal combustion or jet engine come from?

I am trying to understand that why does a piston engine produce vibrations? What is the source of it and how will it cause the whole internal combustion engine to vibrate in response? Will jet engines ...
34 views

### How would a realistic PV diagram look for a Beta-Type Stirling Engine?

Normally, most textbooks use the diagram below to describe an ideal Stirling Cycle. 1st comes isothermal expansion of gas, 2nd comes isochoric heat transfer to the regenerator, 3rd isothermal ...
1 vote
224 views

### Does the turboprop engine torque get transferred to the engine mount and ultimately aircraft when engine is active?

When the turboprop engine is active, the propeller shaft rotates and causes the propeller to rotate as well, which in turn generates thrust. The propeller shaft rotates because of the torque (or ...
2k views

### Alcohol as a working fluid?

Alcohols with their lower boiling point and overall non-toxicity, could they be used as a turbine working fluid instead of steam water?
77 views

### Why doesn't the aircraft propel forward when on ground and the engine is running?

For a car, we know that we need to use the gear system in order to move the car forward. For the aircraft, I don't know if there exists any gear system within it? I have seen aircrafts staying at the ...
145 views

### Out of the three types of Stirling Engines, which one is the most efficient and delivers the most amount of power?

I was thinking that the beta Stirling engine would be the most efficient as it has a displacer to block heat transfer from the hot to cold regions in between thermodynamic cycles. However, I heard ...
83 views

### What are the benefits of reducing valve duration in an engine?

From my understanding this would be beneficial if you've taken a stock engine and put a smaller, more restrictive air intake on it. It would also be done to create more low end torque which shifts the ...
1 vote
53 views

### Could engines run on 1 cylinder while idling to save fuel?

Could engines run on 1 cylinder while idling to save fuel? And then either each "idle" session alternate a different cylinder so wear and tear is even, or change the active cylinder ...
7k views

### How many power strokes per rotation in a 3 cylinder engine?

How many power strokes occur for every complete rotation in a regular 3-cylinder engine? Or in other words, every how many degrees does a new power stroke takes place? Does anyone know please?
1 vote
95 views

### Theoretical maximum pressure from combusting LPG

I am curious how to find or estimate the theoretical maximum pressure that the combustion of a LP gas, such as propane, can produce inside of a constant volume, such as in a cylinder. I know what the ...
24 views

### at what point is increasing pressure ratio diminishing in returns?

piston engines of ww2 planes had pressure ratio of at least 10, while jet engines were still vastly superior with a pressure ratio of only 3. Certainly pressure ratio of 1 would bring 0% fuel ...
103 views

### Replicate stepper motor with gasoline engine

For those unaware of what a DC stepper motor is, it boils down to an electronic motor where the rotation can be precisely controlled, i.e. you can control the rotation of the motor in fractions of a ...
30 views

### Could you use anything as a fuel source for an engine or motor, if it's designed to use that specific type of fuel?

By anything I don't mean to put some random liquid in a car engine, but is it possible to design and build an engine or motor that could use something like tea or orange juice for it's fuel? I know it ...
563 views

### Why is soot produced in diesel exhaust, since diesel runs lean?

Since diesel runs lean, why is soot produced in diesel exhaust? Soot is carbon particles due to incomplete combustion. But, since diesel runs lean with plenty of oxygen, why does this happen?
3k views

### Why do some diesel engines run on diesel fuel and others on fuel oil?

Trucks and smaller vehicles with diesel engines run on diesel fuel which looks more or less like kerosene - less flammable than gasoline, low viscosity liquid. However larger diesel engines like this ...
176 views

### In a diesel engine, does more heat leave the engine through the tailpipe or the radiator?

Diesel exhaust is hot, and there's a lot of it. Diesel radiators also get pretty hot. In a typical diesel engine, which one is dissipating more heat? EDIT: In response to a request for specificity ...
2k views

### Are small car engines designed to tolerate a higher duty cycle than large car engines?

For simplicity we're going to ignore aerodynamics and vehicle mass for a moment... Are small (around 1 litre) car engines designed to tolerate a higher duty cycle than large (2+ litre) car engines? ...
30 views

### Relation between engine size and its power to weight ratio

Is there a relation between engine size and its power to weight ratio? For example if you shrink the engine to half the size will it have exactly half the power?
1 vote
3k views

### Why does a radial engine need a master rod?

Why does a radial engine need a master rod? Why can't slave rods be the only rods? Would this spider bearing (around 1:05 in the video) work for an IC engine, why or why not?
30 views

### Understanding a Variable Lift Valve Train Patent

So my father has this patent, and I'm not entirely sure how a certain aspect of it is supposed to be working. I understand how it can be useful, but I don't understand how such a seemingly simple ...
4k views

### Is there a reason (in terms of the physics involved) why it is better to push start a car in 2nd gear rather than 1st?

I am struggling to understand why it is recommended to push start a car in 2nd gear rather than 1st - in terms of the physics involved, I fail to see a reason why this would be the case. I have ...
79 views

### Why do custom engines typically specify a type like "Ford" or "Chevy"?

I notice that when custom car engines are sold they nearly always have a big name type name like "Ford" or "Chevy". Is this because the block and crankshaft comes from those companies and the custom ...
1 vote
21 views

### Ignoring Mechanical Material Properties and Design Implications, in a Compressor, does the Thermal Density of the Blades Affect Efficiency?

Consider an ideal adiabatic compressor, ignoring the remainder of the thermodynamic cycle. In this case, the heat flow q into and out of the compressor itself is zero, by definition of adiabatic ...
223 views

### When does the minimum temperature in a four-stroke cycle occur inside the engine cylinder?

I've checked on quite a few places on the net and some say it occurs at the beginning of suction stroke and others say at the end of suction stroke. I believe it to be at the end of suction stroke ...
1 vote
1k views

### Can an electric motor use reciprocating pistons like an internal combustion engine does?

Would it be possible to have an electric motor that uses an electromagnet to force a piston up and down to turn a shaft, similarly to an internal combustion engine, but without burning fuel? Is there ...
52 views

### Relationship between Heat Flux and Engine RPM

I'm doing a project that involves knowing the average steady-state heat dissipation rate of a single cylinder air-cooled engine (through the engine wall and fins) at a given RPM. The problem is that I ...
52 views

### What developments made diesel engines suitable for personal cars in the 1970s/1980s?

Both diesel and gasoline engines were developed in the late 19th to early 20th century. Diesel engines were for the most part of the 20th century used mostly for large applications in ships, trains, ...
80 views

### Effect of Pressure on Combustion efficiency (of hydrogen) in excess air

Can somebody explain relation between combustion efficiency and pressure in lean mixtures using any kind of chart or mathematical equations? At first glance I thought, combustion efficiency increases ...
69 views

### How do turboshaft engines maintain a constant rpm regardless of load?

I understand that most turboshaft engines tend to run at (or close to) their most efficient rpm all of the time, and it is the load that is changed e.g. the pitch of the blade pitch on helicopters. ...
73 views

### What are the non-practical features of a sterling engine that cause the internal combustion engine to be used instead?

What are the non-practical features of a sterling engine that cause the internal combustion engine to be used instead (in a car)? (e.g. price, size, the power to weight ratio, etc.) Can you name any ...
1 vote
39 views

### Efficiency of an engine

What is meant by thermodynamic efficiency of an engine? and what are the factors that affect the thermodynamic efficiency of a diesel engine?
29 views

This may be difficult to answer but, theoretically, if you had a car with a sterling engine that produces say approximately 300 horsepower how much of any specific heat source would need to be used if ...
311 views

### What's the slowest airflow speed a ramjet could work?

Thinking experiment about a flying device having the fewest moving parts, whats the slowest cruise speed achievable using a ramjet, no matter the scale of this device. Working altitude is troposphere. ...
1 vote
324 views

### How do external irreversibilities decrease the efficiency of thermodynamic cycles?

In gas power cycles, one mentioned that: The Carnot cycle is both externally and internally reversible. Therefore making the Carnot cycles more efficient than other practical cycles. Question: ...
1 vote
111 views

### How difficult would it be to build an entire engine (block and all) in 16th century conditions?

I was ruminating over A Connecticut Yankee in King Arthur's Court. In the book, a trained American engineer goes back in time and creates guns. The book itself predates tanks, but one could imagine ...
3k views

### Manual transmission: Why downshifting is less smooth than shifting up?

Today while driving I had to make a quick shift to a lower gear that was not as smooth as it should've been. I've been taught that while shifting to a lower gear you have to be more careful when ...
157 views

### Inlet of an ICE [closed]

What is wrong with totally replacing the inlet of a piston engine with a surgical mask?As surgical masks get rid of about 80% of air impurities and dusts.