Basic theory of compressed air to power and power

The basic theory of compressed air (3)

Power and power

(energy consumption ratio and volume ratio)

1, the compressor efficiency

Volumetric efficiency is the actual capacity of the compressor and the theory of the ratio of gas volume, expressed as a percentage.

Quantitative gas compression efficiency is compressed to the ratio of the actual’s theory of power and the power needed. The theory of power according to working condition of isothermal or adiabatic condition to calculate. The corresponding percentage compression efficiency can be used to determine and presentation. In terms of a compressor driven by steam drive or internal combustion engine, mechanical efficiency refers to the compressor indicated work points and on the shaft brake horsepower Ma Lizhi ratio. In the case of a compressor motor drive, mechanical efficiency refers to the indicated power compression cylinders with the ratio of the shaft power of compressor. In percentage terms.

2, the overall efficiency

Overall efficiency is the sum of compressor compression efficiency and mechanical efficiency.

Compressor shaft power, braking power include: gas compression work - indicated work, friction work

Ni

Mechanical efficiency eta m =

Nad

Rough estimate: Nad = 1.634 PjVm (k/k - 1) [epsilon)/k (k - 1-1] Kw

N = N motor shaft/eta, eta preach (belt: 0.92 ~ 0.98, the gear: 0.97 ~ 0.99)

The screw compressor, air compressor shaft power with the power of the fan motor.

3, volumetric ratio can

Can volume ratio refers to the compressor suction unit volume in unit time consumed power, usually expressed in Kw/M3 / min, under pressure from the same exhaust volume than can the smaller. The low power consumption. The compressor efficiency is the true measure of the efficiency of the compressor.

Rating: regulate conditions: Pj = 1 bar (A), tj = 20 ℃, bits of = 0, t = 15 ℃ water

Pc = 7 bar (table), water or less 2.5 L/M3

Power is the work done per unit time, such as the power (kw) is classified as 76 kg - m/h

Power is the conversion of energy in the measure.

In order to get the cost of power, we must also include time, for example: instead of kw KWH cost money.

Get horsepower and converts it into the user’s cost, we want to use the following formula:

Motor brake horsepower x 0.746 (converted to kw) power cost hours * * years

Annual cost = -

The motor efficiency

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Noise and voice assessment

Is considered to be noise nuisance or interfere with the voice.

Fully prepared to sit all night discos, while smoking and enjoy up to 95 decibels of disco music, but incredible is that he can’t stand the morning of the second day of the 65 decibels of noise copier. The noise of the user like disco and don’t like the noise of the copier. A typical cocktail party value is 90 db noise, rock band from 100 to 138 decibels of noise.

So what is the db?

Db can be interpreted as the definition of the two kinds of energy ratio logarithmic (with 10 at the bottom) multiplied by 10.

W2

The dB = 10 log -

W1

Add 10 decibels increased energy 10:1, 20 decibels energy increases 100:1, increasing 30 decibel, 1000:1.

For our application, we discuss the sound power level - set of W1 reference value for 10 to 12, the formula becomes:

PWL (dB) = 10 log W / 10-12

For example, if we have a sound source, send a 10-5 watts of power level, the sound power is:

Ten to five

PWL = 10 log - = 70 db

10-12

When his back to the ear noise, it was found that the ear can automatically "hear" the low frequency noise, network is very similar to the following "A" level.

To this end, the standards of industrial noise measurement choice is "A" level noise level, and use the dBA terms.

Due to the reflection noise can easily test probe capture, so set up another standard. The standard requires that all noise measurement under the condition of the "open field".

Measuring gas equipment sound ANSIS51 rule points out: the noise should be one meter away from the machine, measuring one point five meters high.

So, here we confirmed the test probe position and measure the location and grade "A" network measurement noise.

All manufacturers use the same basic rules of measurement noise.

If two of the same noise level machine run side by side, the result of the noise level will be increased by 3 dba (two times)

For example: in our original formula:

Ten to five

PWL = 10 log - = 70 db

10-12

If we redouble our sound power level to 2 x 10-5

2 x 10-5

PWL = 10 log - = 73 dB

10-12

A compressor manufacturer statement: noise level guarantee + 3 dba is to point to the noise level will be its double the level of noise or statement by half.

Two operating units at different rates, may have the same noise level, but the sound is totally different. One might be more harsh than another. This is because the noise is based on the spectrum from all frequencies in addition a number to form the dBA.

As the measurement noise level, will measure to each octave band noise, with an "A" and assess and phase to answer (dBA) are obtained.

What all this means that:

1, this means that, due to the reflection we can’t put a compressor in the room, and then expect to have and in the open field under the condition of the same noise level.

2, we can’t smooth by two different units (at a different speed, different drive, the different components and different shell) can make an intelligent guess to noise level. Measurement noise is the only way is to use a sound measurement device.

How do we overcome the noise level in the obvious differences?

1, through accurate measurement noise level

2, through the know how noise level of the difference of themselves, to specify the frequency and the noise of factors.

3, know two have the same noise level, but the unit noise with different frequency characteristics to the damage of the ear is the same, even if one of the "sounds" definitely more lighter.

How can we further reduce the noise?

1, the body of all the joints are safe, forklift hole closed, the unit on the surface of the substrate is enclosed.

2, through the pipe inlet and exhaust.

3, reduce the reflection noise.

Sound and noise measurement is only at best a very not an exact science. For this topic discussion, hoping to avoid the wild field of fixed fee and are not satisfied with the user.

1, all the noise level measurement using ANSLS51 standards. This is an industry standard. We should be referenced by the standard reference used in the noise level. Short said, the standard requires an empty field measurement (no reflection wall and roof), units around the multi-point measurement, and the measured value averaged. Should be outside the unit one meter, measuring one point five meters of ground and foundation level. Any single point measurement can reference A noise level. As long as the average reading can meet or below the reference level. In addition, the measure noise measurement is should be adopted by the average of the broad band. When asked or given should take frequency analysis, some frequency band of readings can and usually is higher than average noise measure. Again, points out that this is a standard.

2, in the standard structure without giving and tolerances shall apply

3, no real place in the field of units should write the "open field". Actually rules where the noise level is always higher, because from the nearby walls or roofs and nearby equipment distribution of reflection.

4, may submit the noise level of data is when measuring should be specific compressor using the actual measurement and get in a same type compressor double running under the same conditions can be interpreted as a typical noise level.

The attention

For any more or repeated compressor measurement, has the certain error. These errors are pointed out in order to guarantee the noise levels for a specific problem of compressor, should add 3 db on the total dBA measure value. When the noise level guarantees to give a user, to obey the above requirements is absolutely necessary.

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Empirical formula

A 0.7 MPa 0.1416 M3 per horsepower production volume of air compressor

Every 0.007 MPa pressure ｄｒｏｐ equal to 0.5% power

The thermal load of air compressor = HP x 2545 btu/(1.055 KJ btu = 1)

Water-cooled compressor GPM (water liter per minute)

HP x 2545

500 x delta T water

Or, if the water delta T = 11.1 ℃ (closed loop), HP / 4

Such as delta T = 22.2 ℃ water, city water supply system) for HP / 8

65% of the condensed water after after cooler has been removed

After freezing type dryer, 96% of the condensed water has been removed

Exhaust temperature rise every 11 ℃, water content will be doubled

0.028 gallons per 0.028 M3 = = 28.31 liter = 1 cubic feet

Air compressor must with 133.5 litres per M3 air inflow cylinder gas storage capacity

Is derived from the ideal gas law formula of pump gas

Volume (m3) x pressure rise (MPa)

Time (in) = -- -- -- -- -- -- -- --

Volume (m3) x 0.1013 (MPa)

The motor pulley size (inches) x compressor speed (RPM)

Motor pulley size (inches) = speed (RPM)