-a single cylinder reciprocating pump capacity
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Analysis of directing-acting steam reciprocating pumps
-Indicator pressure diagram: Discharge from pump is pulsating and changes
only when speed of pump is changed. Often air
chamber is connected on pump discharge to
provide more even flow by evening out pressure
surges. The pump consists of steam cylinder end in
line with liquid cylinder end, with a straight rod
connection between steam piston and pump piston
or plunger. These pistons are double acting which
means that each side pumps on every stroke.
Another construction style is the power pumps
which convert rotary motion to low speed
reciprocating motion using a speed reducing gear.
Power pump can be either single or double-acting.
A single-acting design discharges liquid only on
one side of the piston or plunger. Only one suction
and one discharge stroke per revolution of the
crankshaft can occur as shown in figure. The
double-acting takes suction and discharges on both
sides of the piston resulting in two suctions and
discharges per crankshaft revolution. Power pumps
are generally very efficient and can develop high
pressures. These pumps are more expensive than other pump types.
-A Single Cylinder Reciprocating Pump Capacity:
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For a Triplex Pump:
Prove analytically that:
Qmax/Qmean=π/3=1.047
(as given in above figure).
In the next figure, we note
that the constant K=Qmax.
If we examine the figure,
We see that the total Q has
a repeated cycle every 60o.
We can get Qmean by doing
integration for the function
of Q(θ) over any 60o
part
part and divide by that base
of length L = 60 * (π /180)
So, we can write:
����� ∗ L = (�� + ��)�� �� ����� ∗ L = (��)�� �� ����� ∗ L =���
��
��
� (�� + ��)��
���
���
By doing the first integral, ����� ∗ L = � � sin � �� + � sin(� − 240)�� ���
����� ∗ !� = [−� #�$� ]��� − [� cos(� − 240)]��� = −K[(cos60 − cos0)] − K[(cos(−180) − cos(−240)] = K
So we get: Qmean= 3K/π ; but since Qmax= K
The ratio is therefore: Qmax/Qmean= π/3 = 1.047 as shown on the figure.
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