Sensor system for sensing the mass concentration of particles in air
The present application relates to sensor systems for sensing mass concentration of particles smaller than a predetermined threshold in an air stream. Such systems may include an inlet (for receiving a total flow of air with particles) connected to a first splitter (for separating the total flow into a major flow and a minor flow), a joint where a first duct carrying the major flow and a second duct carrying the minor flow come together, and a sensor in the first duct for measuring the amount of particles smaller than the predetermined threshold in the major flow.
1. A sensor system for sensing mass concentration of particles smaller than a predetermined threshold in an air stream, comprising:
an inlet for receiving a total flow of air with particles, the inlet connected to:
a first splitter
for separating the total flow of air into a major flow and a minor flow;
the major flow comprising particles smaller than the predetermined threshold;
the minor flow comprising particles larger than the predetermined threshold; and
for leading the major flow to a first duct; and
for leading the minor flow to a second duct;
a joint, wherein the first duct and the second duct come together, and an outlet, coupled to the joint;
a sensor, arranged in the first duct for measuring an amount of particles smaller than the predetermined threshold comprised in the major flow;
a first flow fan for drawing the total flow through the system; and
a second flow fan for drawing the major flow through the first duct.
2. The sensor system according to claim 1 , wherein the second flow fan is arranged in the first duct.
3. The sensor system according to claim 2 , wherein the first flow fan and the second flow fan are configured to draw the total flow and the major flow such that a ratio of a flow rate of the major flow to a flow rate of the minor flow is smaller than 1.
4. The sensor system according to claim 2 , comprising a controller for controlling the first and the second fan speeds, wherein the flow rate of the major flow and the flow rate of the minor flow are constant, wherein the first flow fan and the second flow fan are configured to draw the total flow and the major flow such that a ratio of a flow rate of the major flow to a flow rate of the minor flow is smaller than 1, wherein the first splitter is a virtual impactor or a cyclone filter.
5. The sensor system according to claim 4 , wherein the sensor comprises:
an optics chamber, enabling an air flow to trespass;
an electromagnetic radiation source, for generating a light bundle through an area of the optics chamber for trespassing air;
a photon collector, for collecting light scattered by particles in the trespassing air flow.
6. The sensor system according to claim 5 , comprising a second splitter unit, arranged in the first duct, upstream from the sensor, wherein the second splitter unit is arranged for creating:
a sample flow; being a central flow; and
a sheath flow; being a coaxial jacket.
7. The sensor system according to claim 1 , comprising a controller for controlling the first and the second fan speeds.
8. The sensor system according to claim 1 , wherein a flow rate of the major flow and a flow rate of the minor flow are constant.
9. The sensor system according to claim 1 , wherein the first flow fan and the second flow fan are configured to draw the total flow and the major flow such that a ratio of a flow rate of the major flow to a flow rate of the minor flow is smaller than 1.
10. The sensor system according to claim 1 wherein the first splitter is a virtual impactor or a cyclone filter.
11. The sensor system according to claim 10 , wherein the first splitter is a virtual impactor and comprises: a first splitter inlet defining a first direction of the total flow and a first splitter outlet comprising a fork into at least a first branch connected to the first duct and a second branch connected to the second duct, wherein the first branch and the second branch are oriented such that an angular change in flow direction from the first direction to the first branch is larger than an angular change in flow direction from the first direction to the second branch.
12. The sensor system according to claim 1 , wherein the first splitter comprises a parallel branch and a perpendicular branch, for splitting the total flow in: the major flow that leads to the first duct via the perpendicular branch; and the minor flow that leads to the second duct via the parallel branch.
13. The sensor system according to claim 1 , wherein the sensor comprises:
an optics chamber, enabling an air flow to trespass;
an electromagnetic radiation source, for generating a light bundle through an area of the optics chamber for trespassing air;
a photon collector, for collecting light scattered by particles in the trespassing air flow.
14. A sensor unit, comprising a housing and two of the systems according to claim 13 integrated in the housing, wherein the respective electromagnetic radiation sources are one and the same device, and wherein the unit comprises a beam splitter, for receiving a light beam from the radiation source, and for splitting it into two beams, which are used in the respective systems.
15. The sensor unit according to claim 14 , comprising a processing unit configured for comparing an amount of particles measured in each of the two systems.
16. The sensor unit according to claim 14 configured to:
receiving an air flow from outside a vehicle in the inlet of a first one of the two systems;
receiving an air flow from inside the vehicle in the inlet of a second one of the two systems;
comparing an amount of particles measured in the air streams of the two systems.
17. The sensor unit according to claim 16 , selecting one of the air streams for ventilating the vehicle.
18. The sensor system according to claim 1 , comprising a second splitter unit, arranged in the first duct, upstream from the sensor, wherein the second splitter unit is arranged for creating:
a sample flow; being a central flow; and
a sheath flow; being a coaxial jacket.
19. The sensor system according to claim 18 , wherein the second splitter comprises:
a first hollow tube, and a second hollow tube, enclosing at least a part of the first hollow tube;
a second splitter inlet, providing incoming air an essentially unimpeded entrance to the first hollow tube and providing incoming air a parallel entrance to the second hollow tube via a filter.
20. A vehicle comprising a first one of the sensor system according to claim 1 .
21. The vehicle of claim 20 , comprising a second one of the sensor system, wherein the inlet of the first one of the sensor systems is connected to an outside of the vehicle and the inlet of the second one of the sensor systems is connected to the inside of the vehicle.