Pressure and torque relationship

Basics of Force, Torque and Pressure | Sushma Industries

pressure and torque relationship

Torque is the outcome of cylinder pressure, which in turn depends on volume or rather mass of air ingested, compression ratio and combustion temperature. Use this equation to determine the torque created by a hydraulic motor with respect to the motors displacement. PSI is pressure difference across motor. Basics of Force, Torque and Pressure. Force -Definition. A force is a push or pull upon an object resulting from the object's interaction with another object.

It is important to recognize that while maximum torque and horsepower are useful general specifications, they are of limited use when making calculations involving the overall motion of a vehicle.

This is because in practice both vary as a function of rotational speed. The general relationship can be non-linear and differs for different types of motor as shown in Figure 4. In internal combustion engines the combustion pressure and temperature increase with rotational speed. An optimum combination of these variables occurs at a specific rotational speed, leading to the observed peak in available torque.

Relationship of available torque to rotational speed for different sources. How can we increase or decrease torque? It is often necessary to increase or decrease the torque produced by a motor to suit different applications.

Recall that the length of a lever can increase or decrease the force on an object at the expense of the distance through which the lever must be pushed. Similarly, the torque produced by a motor can be increased or decreased through the use of gearing.

pressure and torque relationship

An increase in torque comes with a proportional decrease in rotational speed. In fact, in cars of equal weight, the smaller engine will probably race BETTER because it's much lighter, therefore puts less weight on the front end. AND, in reality, the car with the lighter 2-liter engine will likely weigh less than the big V8-powered car, so will be a better race car for several reasons.

Measuring Power A dynamometer determines the POWER an engine produces by applying a load to the engine output shaft by means of a water brake, a generator, an eddy-current absorber, or any other controllable device capable of absorbing power. Then it applies various factors air temperature, barometric pressure, relative humidity in order to correct the observed power to the value it would have been if it had been measured at standard atmospheric conditions, called corrected power.

Power to Drive a Pump In the course of working with lots of different engine projects, we often hear the suggestion that engine power can be increased by the use of a "better" oil pump.

Implicit in that suggestion is the belief that a "better" oil pump has higher pumping efficiency, and can, therefore, deliver the required flow at the required pressure while consuming less power from the crankshaft to do so. While that is technically true, the magnitude of the improvement number is surprisingly small.

pressure and torque relationship

How much power does it take to drive a pump delivering a known flow at a known pressure? We have already shown that power is work per unit time, and we will stick with good old American units for the time being foot-pounds per minute and inch-pounds per minute.

pressure and torque relationship

Since flow is more freqently given in gallons per minute, and since it is well known that there are cubic inches in a gallon, then: Since, as explained above, 1 HP is 33, foot-pounds of work per minute, multiplying that number by 12 produces the number of inch-pounds of work per minute in one HPDividingby gives the units-conversion factor of Therefore, the simple equation is: When the equation is modified to include pump efficiency, it becomes: So suppose your all-aluminum V8 engine requires 10 GPM at 50 psi.

The oil pump will have been sized to maintain some preferred level of oil pressure at idle when the engine and oil are hot, so the pump will have far more capacity than is required to maintain the 10 GPM at 50 psi at operating speed. That's what the "relief" valve does: It is actually pumping roughly 50 GPM 10 of which goes through the engine, and the remaining 40 goes through the relief valve at 50 psi.

The power to drive that pressure pump stage is: That pump at the same flow and pressure will consume: General Observations In order to design an engine for a particular application, it is helpful to plot out the optimal power curve for that specific application, then from that design information, determine the torque curve which is required to produce the desired power curve. By evaluating the torque requirements against realistic BMEP values you can determine the reasonableness of the target power curve.

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Typically, the torque peak will occur at a substantially lower RPM than the power peak. For a race engine, it is often beneficial within the boundary conditions of the application to operate the engine well beyond the power peak, in order to produce the maximum average power within a required RPM band.

pressure and torque relationship

However, for an engine which operates in a relatively narrow RPM band, such as an aircraft engine, it is generally a requirement that the engine produce maximum power at the maximum RPM. That requires the torque peak to be fairly close to the maximum RPM. For an aircraft engine, you typically design the torque curve to peak at the normal cruise setting and stay flat up to maximum RPM.

Basics of Force, Torque and Pressure

That positioning of the torque curve would allow the engine to produce significantly more power if it could operate at a higher RPM, but the goal is to optimize the performance within the operating range. An example of that concept is shown Figure 3 below. The three dashed lines represent three different torque curves, each having exactly the same shape and torque values, but with the peak torque values located at different RPM values.

pressure and torque relationship

The solid lines show the power produced by the torque curves of the same color. Again, moving the same torque curve to the right another RPM blue, lb-ft torque peak at RPM causes the power to peak at about HP at RPM Using the black curves as an example, note that the engine produces HP at both and RPM, which means the engine can do the same amount of work per unit time power at as it can at The RPM band within which the engine produces its peak torque is limited.