Axial and Mixed Pump Theory

Axial Pump
Axial Pump

Unlike the centrifugal pump, the performance in axial machines is a function of the action of the blade profiles. Because of this, the main approach in design of axial pumps is focused on blade performance.

Impeller blades of axial flow pumps have a double curvature form at the inlet and at the outlet due to the change in diameter from hub to periphery. Absolute flow before and after the impeller and relative flow along the impeller passage are axisymmetric and potential. There is no radial mixing. Under this condition, each streamline is parallel to the axis of the pump. Fluid passes parallel to the pump axis i.e., along the streamline. Continue reading “Axial and Mixed Pump Theory”

Criteria for Selecting Pumps – Specific Speed

We had a great week last week with our Steam and Gas Turbine Design workshop and we thank all of our participants who joined us in Boston and Zug, Switzerland! But like any rotating turbomachinery company, we’re rotating right along into another topic, pumps.

As with any turbomachine, when you’re in the process of selection, you should take into account a few factors depending on the application.

The specific speed should be the first parameter to take into account when designing and installing a new pump. Continue reading “Criteria for Selecting Pumps – Specific Speed”

A Common Debate: Axial or Radial Turbine?

Comparison of efficiency against power output for axial flow and radial inflow turbine configuration
Comparison of efficiency against power output for axial flow and radial inflow turbine configuration

The question always remains, which is better: axial or radial? But with that question are sub questions: Which application? Which fluid? What results are you looking for exactly?

In automobiles for waste heat recovery, we believe that radial inflow turbines are more suited for use. Here’s why:

Continue reading “A Common Debate: Axial or Radial Turbine?”

3 Categories and Sources of Vibrations

In view of the large number of blades in any turbine machine, the existence of unavoidable sources of vibration excitation and the serious consequences of the failure of just one blade, an intimate knowledge and understanding of the vibration characteristics of the blades in their operating environment is essential.

Vibration excitation can arise from a variety of sources but principally involves the following categories: Continue reading “3 Categories and Sources of Vibrations”

Retrofitting – Why Turbine Seals Are Important

Wreckage of 330 MW Turbine-generator from LP rotor burst
Wreckage of 330 MW Turbine-generator from LP rotor burst

Whether it is caused by a “poor” design, extreme operating conditions or even too much deterioration, turbine failures can occur. In order to help prevent these it is necessary to perform regular maintenance on all parts of the machine and control the conditions at which the turbine is operating at any moment in time as well as performing repairs and retrofits to keep the pieces in good shape.

One way to improve steam turbine efficiency is through better seals. However, when designed incorrectly they can create significant damages and performance losses in the turbine. Sealing steam turbine rotors presents several challenges. Any gap between the rotor and the packing lets the steam escape, dropping the pressure and wasting energy. If the packing ring is too tight, however, the rotor will rub, which creates localized hot spots. Continue reading “Retrofitting – Why Turbine Seals Are Important”

Carryover Losses – Steam and Gas Turbines

losses
Losses

A number of loss prediction methods exist in turbomachines. Concerning axial turbines, there are at least seven methods just for cascade losses! But there are also loss models developed to predict individual loss components such as secondary, seal and tip clearance losses and more.

Of course depending on the machine and application type, some of the models are more or less applicable to specific cases. But ff the different types of auxiliary losses, which are losses that do not belong to blade cascades and can be classified as whole stage, there are carryover losses.

Continue reading “Carryover Losses – Steam and Gas Turbines”

Working Fluid in Organic Rankine Cycles

orcfluid
ORC Fluid

The choice of the working fluid for any given application is a key issue and should be done based on specific applications to achieve maximal efficiency. For working fluids in ORC, a green energy alternative, there are some requirements to keep in mind:

•Thermodynamic performance
Low pump consumption and high critical point

•Positive or isentropic saturation vapor curve
Avoid wetness in flow path, i.e. avoid damages of flow path elements

•High vapor density
Decrease sizes of equipment (expander and condenser)

•Acceptable pressures
High pressures usually lead to higher investment cost and increasing complexity

•High stability temperature
Prevent from chemical deterioration and decomposition at high temperatures

•Low environmental impact and safety level
•Good availability and low cost Continue reading “Working Fluid in Organic Rankine Cycles”

At a Glance – Turbochargers

turbocharger
Turbocharger

With the ongoing movement toward global environmental protection, regulations related to the exhaust emissions and fuel consumption of automobiles are being strengthened. To cope with these requirements, turbochargers are an effective tool to improve fuel consumption and reduce carbon dioxide emissions, by reducing the engine weight and friction loss.

Since a turbocharger supplies compressed air to an engine, it can reduce the engine displacement relative to an atmospheric engine for the same power. Variable geometry turbochargers, which can control the boost pressure according to the engine operating conditions, are becoming increasingly popular, creating a demand for a centrifugal compressor with a wide and stable operational range. Continue reading “At a Glance – Turbochargers”

Facts About Waste Heat Recovery for IC Engines

icengines
ICengines

Last month we hosted a webinar on waste heat recovery for internal combustion engines and beyond. You can view the webinar here.

This is becoming an increasingly popular topic in our industry and we’re seeing more information being posted from other industry professionals, so we thought this would be a great time to explain some basics about this energy efficient technology.

The situation:
A large part of the energy produced in an IC engine is lost to the surroundings but the waste heat from the engine exhaust and coolant is still an attractive energy source that reaches around 60% of the total energy converted from fuel. Continue reading “Facts About Waste Heat Recovery for IC Engines”

What’s An Ideal Heat Engine Cycle?

The Carnot cycle is the most efficient cycle possible for converting a given amount of thermal energy into work or, conversely, for using a given amount of work for refrigeration purposes.

Every thermodynamic system exists in a particular state. A thermodynamic cycle occurs when a system is taken through a series of different states, and finally returned to its initial state. In the process of going through this cycle, the system may perform work on its surroundings, thereby acting as a heat engine. Continue reading “What’s An Ideal Heat Engine Cycle?”